1. Field of the Invention
This invention relates generally to a tire molding mold, and more particularly to a tire molding mold comprising a mold body having an inner circumferential surface corresponding to the contour of a tire being molded, including the tread thereof, and a mold attachment for molding recesses of the tire being molded, and the manufacturing method of the same wherein the mold body and the mold attachment are manufactured separately and the mold attachment is adapted to be detachably fitted to the inner circumferential surface of the mold body so as to permit the tire tread pattern to be changed without replacing the mold body with a new one.
2. Description of the Prior Art
In general, a tire molding mold has a pattern corresponding to the contour of a tire being molded, consisting of a tread portion 1 corresponding to the tread of the tire being molded and projections 2, or ribs and/or lugs, corresponding to recesses on the tire tread, as shown in FIG. 1. As is well known, the maneuverability, travelling, road holding, noise reduction and other performance of a tire are determined by the pattern and dimensional accuracy of the tread portion 1 and the projections 2.
Heretofore, the tire molding mold has been manufactured by integrally molding the tread portion 1 and the projections 2, or welding the projections 2 in advance onto the inner circumferential surface of a mold constituting the tread portion 1, using the plaster molding, sand casting, ceramic casting, metal mold casting or other precision casting process, the engraving process, or the electrical discharge machining process. These conventional manufacturing methods necessitate the replacement of the entire metal mold each time the tire tread pattern is changed to improve the aforementioned ioned tire performance. Furthermore, vent holes and other venting means have to be provided by machining the mold separately. With the conventional methods, it was impossible to manufacture a tire molding mold with as high concentricity and roundness accuracies as within 0.1 mm. In addition, the finish machining of metal molds involves an enormous amount of manhours, leading to increased manufacturing costs and long manufacturing time.
A method has also been proposed in which the projections 2 are formed as individual pieces, which are inserted into grooves on the tread portion 1. In this case, however, rubber tends to enter into gaps between the grooves and the pieces during tire molding operation, causing unwanted projections (burrs) on the tire tread surface.